1. Field of the Invention
The invention in general relates to diver underwater breathing apparatus, and particularly to such apparatus supplied with breathing gas from a remote source.
2. Description of the Prior Art
In a "push-pull" type breathing apparatus system, the diver is supplied with breathing gas from a remote source and exhaled gas is returned to the source for CO.sub.2 removal and oxygen replenishment. This type of system increases diver safety and productivity by eliminating the burden and possible danger inherent in closed-circuit back-worn apparatus. The push-pull mode of operation allows the changing of CO.sub.2 absorbent canisters at the source without interrupting the diver's work, and a single atmosphere control system will suffice for several divers supplied from the source.
The duration of a single dive is limited solely by diver endurance rather than by equipment limitations, and check-out time is minimal due to the lack of sensors, electronics, power supply, regulators, pressures, etc. that have to be checked out in other types of equipment.
One type of push-pull arrangement proposed in the past supplied the diving mask of the diver with breathing gas and a return hose from the mask conducted exhaust gas back to the source. This proposed apparatus would not allow the diver to make significant excursions above or below the level of the remote source. Another arrangement, such as described in U.S. Pat. No. 3,370,585, included an inhalation valve and an exhalation valve in conjunction with breathing bags to remedy the deficiencies of the mask proposal.
The present invention allows for a push-pull type of operation wherein the requirement for an inlet demand valve may, if desired, be eliminated as well as the requirement for breathing bags without the sacrifice of high safety standards.